UNITED STATES- Former Vice President Joe Biden formally joined the crowded Democratic presidential contest on Thursday, betting that his working-class appeal and ties to Barack Obama’s presidency will help him overcome questions about his place in today’s increasingly liberal Democratic Party.

Four years Trump’s senior, Biden would be the oldest person ever elected president should he win.

The Republican Party wasted no time seeking to undercut Biden’s record, releasing a video on Wednesday questioning economic growth under Obama and Biden while resurrecting conservative arguments against Obama’s health care law and a failed investment in green energy company Solyndra.

The video ends with the words, “Joe Biden: Backwards, not forwards.” Yet privately, Trump allies have warned that Biden might be the biggest re-election threat given the former vice president’s potential appeal among the white working class in the Midwest, the region that gave Trump a path to the presidency.

The Republican video notably does not argue a Biden candidacy would lead to socialism, as Trump and his backers have said would happen with many in the large 2020 Democratic presidential field.

Biden is paying special attention to Pennsylvania, a state that swung to Trump in 2016 after voting for Democratic presidential candidates for decades.

The episode offered a stark reminder of Biden’s proclivity to gaffes and his long record in public office that has never felt the full glare of the spotlight that comes along with being a presidential front-runner.

While several 2020 Democratic contenders have embraced the possibility of reparations to African Americans for slavery in recent weeks, Biden last month struggled to explain comments he made as a freshman senator in 1975 about the school busing debate.

Biden’s 2020 bid comes four years after he opted against challenging Hillary Clinton in the 2016 Democratic contest.

In a book he wrote about conversations with his dying son, he opened up about the difficult choice to sit out the last presidential race: abandon a careerlong quest for the presidency or lose precious time with a family he’d held together through tragedy, from his first wife’s and his daughter’s deaths in a 1972 car accident to son Beau Biden’s 2015 death from cancer.